In this case, the invention is based on an electromagnetic clamping device with hydraulic assistance. Clamping devices of this type are used for production machines, for example injection molding machines. The clamping device has two clamping jaws on which in each case a part mold of a divided mold is held. A thrust mechanism driven by an electric motor displaces the clamping jaws with respect to each other along a guide device. The first clamping jaw is divided into two part jaws, which can be displaced with respect to each other in the direction of the guide device. The part jaws interengage in such a way that a chamber to hold pressure medium is formed between them. The first part jaw can be displaced along the guide device. The output of the thrust mechanism acts on one of the part jaws. In order to close the clamping device, in a first step the thrust mechanism pulls one part jaw against the second part jaw, pulling the other part jaw with it, and in a second step the thrust mechanism delivers pressure medium into the chamber between the two part jaws, with the first part jaw locked against the guide device. During the closing of the clamping device, the thrust mechanism is loaded in tension. By contrast, during the opening of the clamping device, the thrust mechanism is loaded in compression. In this case, in order to pull the part molds apart, a substantially higher force is required than for the following action of moving apart the clamping jaws bearing the part molds. The thrust mechanism therefore has to be dimensioned in accordance with the high force required to pull the mold apart.